Are there best practices for implementing an asynchronous game engine loop?

Question

I have implemented a game engine loop as follows:

public static Boolean Start ( )
{
    if (hasBoard)
    {
        //  start engine on worker thread
        asyncTask = new AsyncResult ( stopEngine, asyncTask );
        isRunning = ThreadPool.QueueUserWorkItem ( startEngine, asyncTask );

        if (isRunning)
        {
            Console.WriteLine ( "[{0}] Engine started",
                DateTime.Now.ToString ( "hh:mm:ss" ) );
        }
        else
        {
            Console.WriteLine ( "[{0}] Engine failed to start",
                DateTime.Now.ToString ( "hh:mm:ss" ) );
        }
    }

    return isRunning;
}

public static void Stop ( )
{
    Console.WriteLine ( "[{0}] Engine stopping",
        DateTime.Now.ToString ( "hh:mm:ss" ) );

    asyncTask.SetAsCompleted ( null, false );
}

private static void startEngine ( Object task )
{
    while (!( (IAsyncResult)task ).IsCompleted)
    {
        Thread.Sleep ( 10000 );

        Console.WriteLine ( "[{0}] Engine running",
            DateTime.Now.ToString ( "hh:mm:ss" ) );
    }
}

private static void stopEngine ( IAsyncResult iaResult )
{
    //  clean up resources

    Console.WriteLine ( "[{0}] Engine stopped", 
        DateTime.Now.ToString ( "hh:mm:ss" ) );

    isRunning = false;
}

I am using the AsyncResult class recommended by Jeff Richter in his article, Implementing the CLR Asynchronous Programming Model. In order to be able to stop the engine from the UI, the implementation I used was a bit off from the standard asynchronous pattern. This implementation works as expected, but when I divert from a standard practice, I revert to the SO community to ensure I am doing things the right way.

Are there any issues with this implementation that anyone can see?

Answer 1

Since this sounds like a project you have control over, I would suggest you ditch APM and use the Task-based model provided in .NET4. This is the recommended approach for .NET4 instead of APM. The Task class is part of the Task Parallel Library (TPL) but it's great for these basic asynchronous jobs as well.

private CancellationTokenSource cts;

public void StartEngine()
{
    if (cts == null)
    {
        cts = new CancellationTokenSource();
        Task.Factory.StartNew(() => GameLoop(cts.Token), cts.Token);
    }
}

private void GameLoop(CancellationToken token)
{
    while (true)
    {
        token.ThrowIfCancellationRequested();
        Thread.Sleep(1000);
        Debug.WriteLine("working...");
    }
}

public void StopEngine()
{
    if (cts != null)
    {
        cts.Cancel();
        cts = null;
    }
}

Answer 2

I would say that It's implied that tasks are short-lived when using the thread pool since the number of threads in it is limited.

In you case I would use a BackgroundWorker instead since you mentioned winforms. BW handles synchronization for you and are therefore able to update the GUI without using InvokeRequired etc.